Studies On In Situ As Doping P-type HgCdTe By Molecular Beam Epitaxy

Mercury cadmium telluride is the main material of infrared detectors.Arsenic is the best doping object of non-intrinsic doping.MBE is the best method of HgCdTe in situ arsenic doping techniques.The properties of Hgl-xCdxTe material and performance parameters of the material are studied.The main contents of this thesis are as follows:1)The film in situ growth process As-doped was studied.Before the Hgl-xCdxTe film in situ growth on the Ge substrate,arsenic surface was passived,then zinc crystal was oriented,and 7～8μm CdTe buffer layer was grown;In the process of the film arsenic-doped growth,shutter was opening.The fluctuation range can be precisely controlled within ±0.5℃ with the power compensation temperature control mode.2)The effect of arsenic beam was studed.The morphology of As in the Hgl-xCdxTe is mainly composed of As4 cluster structure.When the arsenic beam of the order of 10-8 Torr,the average value of surface macroscopic defect is less than 500cm-2,and the average EPD value is lower than 5×106cm-2.When beam of the order of 10-7Torr,crystal surface observed by atomic force microscopy became rougher.When beam of the order of 10-6Torr,the crystal quality decreased significantly,and the half-width FWHM value was higher more than 150arcsec.3)The influence of doping temperature and growth temperature of substrate surface was studied.The doping temperature changes from 220 0C to 250 ℃,and the doping concentration changes linearly from 1×1017cm-3 to 2.6r1018cm-3.The surface growth temperature of the substrate decreases the surface adhesion coefficient of As.When the growth temperature is 190 ℃,the concentration was reduced to the background of 5×1015 cm-3of the test.4)The wavelength,composition and thickness were fitted.The wavelength,composition and thickness of the HgCdTe thin film,are fitted as three parameters.5)The annealing process was studied.When heat treatment temperature increases,the quality of the crystal can be improved.The value of the FWHM of the annealed sheet is about 100.The heat treatment causes the diffusion of the impurities to the surface.The reason of the increased arsenic concentration of the surface layer is explaned.The activation rate was above 90%about low concentration As-doped activation and annealing.When the arsenic concentration was 449×1016cm-3 under 440℃ the activation rate was 99.6%.